*error-protect-tests*

This variable has no effect when test code is compiled. When test code
is not compiled, then if the value of this variable is true, each test
is protected from errors. If an error occurs, then that will be taken
as a test failure unless test-error is being used. If the value of
this variable is nil, then if an error occurs
(except in a test-error
form), an error is signaled and a break loop is entered.